Die set bushing and method of assembling a bushing in a die set



Jan. 21, 1964 D.H.GARDNER DIE SET BUSHING AND METHOD OF ASSEMBLING A BUSHING IN A DIE SET Filed June 20, 1961 2 Sheets-Sheet 1 IN VEN TOR.

DONALD HENRY GARDNER A TTORNEV J 1964 D. H. GARDNER DIE SET BUSHING AND METHOD OF ASSEMBLING A BUSHING IN A DIE SET 2 Sheets-Sheet 2 Filed June 20, 1961 INVEN TOR.

DONALD HENRY GARE/v5 W w F M United States Patent 3,118,217 DE SET EUSHWG AND METHOD OF ASSEM- BHNG A EUHENG IN A DIE SET Donald Henry Gardner, Cranston, Rh, assignor te ilarsco Corporation, Harrisburg, Pa", a corporation oi Delaware Filed June 29, 196i, Ser. No. 118,385 8 Claims. (El. 29-1495) This invention relates to punch and die sets, and more particularly to an improved leader pin and leader pin bushing construction for aligning the relatively movable parts of such sets and method of assembling the same.

A punch and die set is an assembly consisting of an upper member called the punch holder or plate and a lower member called the die holder or plate. The lower or under surface of the punch holder and the upper or top surface of the die holder are those on which the punch and die sections of a finished punch press tool are mounted. In use the die holder is clamped to the bed or bolster plate of the punch press, while the upwardly extending punch holder shank is fastened in the clamping hole provided therefor in the sliding punch press ram. The tool is actuated by the reciprocating motion of the ram. Mating guide posts and bushings of an assembled die set assist in maintaining tool alignment during die setting and the operation of the tool in the punch press.

These guide posts and bushings are employed in maintaining the punch and die details in true alignment during ram-produced reciprocatory movement of the punch and punch holder relative to the die and die holder. In conventional constructions, the posts are of plain cylindrical formation and are carried by and depend rigidly in relatively spaced order from associated punch holders.

The life of the punches and dies and the accuracy of the work accomplished are directly aifected by the accuracy of alignment of the respective moving parts of the die set, and more particularly by the manner in which this alignment is retained over a long period of time.

in the past the bushings and the mating guide posts upon which the bushings slide or reciprocate were ordinarily tightly forced into holes drilled into the punch holder and die holder, respectively. Of course, any alignment thus obtained is dependent upon the accuracy with which the holes into which the parts are to be forced have been drilled. It is well known that by the use of ordinary drills, it is hard to provide holes or openings of any reasonable degree of accuracy, and that such holes or openings can be obtained only by either separately reaming or boring the walls of the openings, with the consequent risk of inaccuracy in the separate operations. It was also necessary to grind the guide pins and the mating bushings on centers and arbors, respectively, to insure absolute concentricity of the outside diameter of the guide pin and the outside diameter of the mating bushings. These many and varied manufacturing opera'tions causes inaccuracies in relative alignment of the guide posts and bushing openings in the plates as well as in the center distance between these openings. A range of less than several thousandths of an inch was not ordinarily or easily or economically obtained. This was especially true because of the methods of assembling the guide posts and bushings in their respective plates.

It is therefore an object of the present invention to provide a method of assembling a die set which is not subject to the limitations, difiiculties and costs of manufact ire above discussed, and wherein alignment is more readily achieved.

Another feature of the present invention is the ease with which the bushings may be secured in fixed relation with each other in the plate, so that after the punch holder and die holder are in place and the die set is assembled, the final and accurate adjustment, of the mating bushings with the guide posts in the punch holder, will have been acccnnplishe in the assembling operation.

Still another object of the present invention is to provide a guide post and guide post bushing method of assembly in which a plurality of elements are adapted to be permanently secured together to form a die holder plate with guide posts and/or a punch holder plate with mating bushings.

And a further object of the present invention is to provide a punch and die set in which the respective parts are secured and retained in extremely accurate relative positioning, and wherein such accuracy may be retained over long periods of continual use.

And still another object of the present invention is to provide a bushing, as a floating member in relation to a punch holder and/or a die holder, which will respond to the influence of a master fixture, so as to be located in accurate alignment and distance in a punch holder and/ or die holder.

Other objects of the present invention will become apparent in part and be pointed out in part in the following specification and claims.

7 Referring to the drawings wherein similar characters of reference refer to like parts:

FIGURE 1 is a perspective view of the upper plate or punch holder component of a die set.

FIGURE 2 is a perspective view of the lower plate or die holder component of a die set.

FIGURE 3 is a perspective view of the new and improved punch holder guide bushing.

FEGURE 4 is a perspective View of the new and improved die holder bushing.

FIGURE 5 is a plan view of the new and improved die set.

FIGURE 6 is a front elevational view of FIGURE 5. FIGURE 7 is a sectional view taken on line 77 of FIGURE 5.

FIGURE 8 is a side elevational view of the bushing shown in FIGURE 4.

FIGURE 9 is a plan view of FIGURE 8.

FIGURE 10 is a plan view of the fixture used to assemble the bushings illustrated in FIGURES 3 and 4 with their respective plates or holders.

FIGURE 11 is a front elevational view of FIGURE 10.

FIGURE 12 is a transverse cross sectional view taken on line 1 12 of FIGURE 10.

FIGURE 13 is a transverse cross sectional View taken on line l3-l3 of FIGURE 10.

FIGURE 14 is a fragmentary view illustrating one mezms of aligning the ends of the serrations parallel with the axis of the bushing.

FIGURE 15 is a fragmentary cross sectional view illustrating the centering of a bushing in an opening.

Referring to FIGURES l, 2, 5, 6 and 7 of the drawings, reference numeral it? designates the punch holder or up 1' plate of a die set, provided with a shank 1'1, and 12 designates the die holder or lower plate of the same set, said parts being movably positioned with respect to each other by guide pins 13, 14 carried by the die set. Said guide pins l3, 14 being coaxial with and slidable within bushings generally indicated at 15, 16 respectively, carried by the punch holder ll).

According to the present invention the die holder '12 is provided with openings l7, 18 located on a center distance having a variation of approximately ten-thousandths of an inch. (See dimension A, FIGURE 2). That is the accuracy between the center of opening 17 and the center of opening 18 will vary in the drilling of the openings in successive nlates by a. distance equal to ten-thousandths of an inch. it will be noted that the final distance between openings l7, 18 after the bushings are located in the openings can not exceed a variation of one-thousandth of an inch. In toolmalters parlance it would be termed, plus or minus half a thousandth. it will therefore he noted that a set of bushings are going to be located on an accurate center distance and accurate alignment even though the initial openings are inaccurately located. After openings '17 and 18 are provided in die holder 12; there is then provided a bushing, generally indicated by reference character (see FlGURES 4-, 8, 9 and 14), having helical convolutions or serrations 21 on the outside diameter. It has been found to be important to the successful result to be achieved, that these helical convolutions or serrations 2 1 correspond to a number twelve thread size; as established "by the American Society of Automotive Engineers. A number twelve thread gives a depth of tooth or serration of (.0175) one hundred seventy-five ten-thousands of an inch (see dimension 3, FIGURE 9). Thus, there is provided a difference of (.035) thirty-five thousanddis of an inch beta een the major diameter C and the minor diameter D (FiGURE 9). The deoth of tooth, dimension B, provides the latitude necessary for the bushing to center itself in opening 13, for example, by correcting its vertical alignment, line B, FIGURE 2, in opening 13. Number twelve thread A.S.A.E. also positively ident iles the pitch of serrations 21.

It has been found that courser threads or finer threads over a number 12 A.S.A.E. are not satisfactory [for a one inch inside diameter bushing size. Other bushing sizes would obviously require different thread sizes. The finer thread has less depth in the serration, dimension B, and therefore less lateral shift is allowed bushing 20 when forced into opening 18. The coarser thread has greater depth in the serration, dimension B, and such an overabundance of lateral shift for bushing 20, so as to efieot the holding power of the serrations in the wall of the opening into which bushing 29 is forced.

Reference is made to FIGURE 15 wherein a fragmentary cross section of die holder or plate 12 is illus trated with opening 18. Serrations 21 are illustrated in full lines. Dimensions F and G illustrate that the serrations 21 of bushing 29- will bite deeper in one side of the wall of opening 18 in plate 12 than in the opposite side of the wall of opening 18, so as to be accurately aligned on center line E for the maintenance of dimension A as dictated by the posts of a fixture, presently to be described. It is important that the pitch and depth of serrations 21 respond accurately to the fixture about to be described.

It has been found that a bushing having serrations which extend the full length of the bushing, tend to prematurely bite into the wall of opening 18, when pressed into opening I18, so that the bushing 2t and not the furture decided the path of entry of bushing 2 into opening '18. in addition, one of a pair of bushings in a fixture would bite into the Wall of an opening before the other bushing bit into the wall of a companion opening. This was obviously unsatisfactory in the result to be achieved, namely, the location of a pair'of bushings in a die set, with a center distance having a toolmakers accuracy without the time, machinery and toolmakers shill heretofore necessary to provide the whercwithall for such accuracy.

It has also been found, that the provision of a lead surface 23, FIGURE 8, having a smooth contour, do% not overcome the tendency of bushing 2% to seek its own path of entry into opening 18 independent of the guidance of the guide post, presently to be described. 7

In order to provide a bushing (29 which will cooperate to satisfy the objects to be herein obtained, it was found necessary to reduce the initial or entering end of the helical serrations to approximately one half their normal depth.

Cne way this can be ccornplished is illustrated in FIGURE 14. A mandrel 25 is passed through thebus hing 29. The bushing 2% is then presented to a grinding wheel 2'5 with the helical convolutions .21 at an ol (9% degrees) ninety degrees to the grinding wheel. in this manner, the helical convolutions 2d are provided with an entering end 27, dimension H, which is carat lel to the central axis G of bushing Dimension is aproxirnately (.016) ten-theirsandths of inch long. in this manner, as bushing 29 is forced into operl ing 13, the cut back or entering end 27 of serrations 2; enters opening 18 in parallel relation to the opening 18.- As force is applied to bushing 2t "forcing it into otiening bushing 26 rotates and serrations 21 out into the wall of opening 13. The rotation of bushing 2% Plus the force ap lied by the lead post, forces the bushing to locate in the opening on an axis dictated by the lead post because the serrations 201 out a path in plate 12 for the bushing.

It is the pie-selected spiral contour of the serrations 21 on the bushing 2% in cooperation with the depth of the serrations 2:1 and the entering end 27 which permits the bushing to react favorably to the dictates of the lead or guide post as to center distance fA,' the" location of the bushing in plate 12 and the final Shane and size of the bushing when located in plate 12. v g

if serrations are used which are parallel to the center axis (G) of the bushing 26, and not helical in si age or if the serrations are not deep enough, the walls of opening is will cause bushing 2b to become elongated or' elliptical instead of perfectly round. If the serrations 21 are to deep the bushing will become loose in open= ing 18. V

Bushing 2b whenfinally located in plate 12 must have absolute concentricity, an exactness of pre-selected di-' mension on inside diameter 39.

Bushing 29A illustrated in FIGURE 3 and which is finally positioned in punch holder or plate 1% (FIGURE 1) is identical to bushing 2% except a collar 31 is provided on one end of the bushin to provide additional length and support for the bearing area or inside diameter of the bushing. The surface 32 of bushing ZtlA abuts plate 16 when bushing EtlA is located in opening 33, 34 of punch holder lll.

FIGURES 10, 11, G2 and 13 illustrate the fixture used to press bushings 2% or bushings ZiPA into position in the respective plates 12 or 1%. g V

. The fixture, generally indicated by reference character 49, consists of a bottom plate 411 and a toll gilate 42 Fixture 46 is essentially a die set. However, instead of stamping or cutting metal, it is used as an aligning fi: ture constructed to provide absolute parallel alignment between bottom plate 41 and top plate This aligning fixture is used in cooperation with and is actuated by a vertical press. in carrying forward the concept of absolute parallel alignment, bottom plate 41 is provided with tour leader pins, '23, d5, secured therein with the highest degree of mechanical accuracy known to the tool making art. Bottom plate 41 is also provided with four bushings, 47, 4d, 49 and 553.

Top plate 4-2 is provided with four bushings Si, 52, 53, 5-4 which are so located and so dimensioned on the ide diameter to slidingly engage leader pins 43, d4, 45, .0, respectivel Top plane 42 is also provided with four guide posts, 55, 55, 57 and 5% fastened therein, as by means of a drive fit. Guide posts 55, 56 are provided with smooth straight sides or diameters. Guide posts 57 and 5-8 are provided with shouldersdh, 61, respectively. Guide posts 55, 525, 5'7 and 5% slidinaly engage bushings. 4'7, 4%- and 5%, respectively.

The a i'n-ent of guide post 55 with guide post '55,. center line I, and the alignment of guide post 57 with: guide post 5%, center line Y is as accurate as the tool makers art will allow. In the same manner, the center distance, dimension L, and the center distance, dimension M, between guide posts 55, 56 and 57, 53 is as accurate as is mechanically possible to provide. Thus, a set of master guide posts are provided, which will determine the alignment and center distance of bushings 20 in plate 12. and bushings 28A in plate 10.

in operation, die holder or plate 12 having openings 17, it; provided therein, is placed on bottom plate 4-1 with openings 17, 18 in vertical alignment with guide posts 57, 53 respectively (FIGURES l and 12). A bushing 20 will be placed on each or" the guide posts 57, 53. Top plate 4-2 under great pressure, such as provided by a vertical press, will ride on leader pins 43, 44, 45 and 46 through bushings 51, 52, 53, 54 slidingly engaging said leader pins 43, 44, '45 and 4-6, respectively, toward bottom plate 41. This movement, in the direction of the arrows in FIGURES I l, '12 and 13, will cause lead surface 23, followed by the second lead surface, dimension H, to enter opening -17 in reference to bushing on guide post 5 3, the bushing will enter opening 18. Guide posts 57, 53 will dictate and determine the location of bushings 2. in openings 17, 12-, as to center distance and alignment. As the serrations 21 engage the wall of openings 17, 18 bushings 21 will rotate and thereby cut themselves into position in plate 12.

in the same manner bushings ZtlA are placed on guide posts 55, 56 and are inserted in openings 33, 34 in plate with shoulder 32 abutting plate id.

Posts 13, i i are press fitted into bushings 2% after bushings 253' are located in openings 17, 18. This function forms no part or the present invention. t is recited to show the completion of a die et. Posts 13, 14 will slidingly engage bushings Z'ilA in plate 16 to complete the die set structure.

it will be seen that applicant has provided a die set wherein the e: pensive procedure of finishing a drilled opening is eliminated. Also eliminated is the necessity of grinding the guide post and the outside of the mating bushing for concentricity.

The elimination of the grinding of the outside diameter of the bushing permits the bushing to be hardened to a greater degree. Such increased hardness may be by carbonitride hardening. Thus, the inside diameter, or the surface of the bushing subject to wear, is provided with a greatly improved wearing surface.

it will be noted that the art to which this invention is directed deals with minute fractions of an inch or tens of thousandths of an inch. it requires expensive machinery and great manual skill on the part of tool makers to pro vide steel parts with such close tolerances on dimensions. However, since the plates 19, 12 are fabricated from mild steel and the bushings are fabricated from extremely hard steel, it was found that by forcing the hard steel bus; ing into the softer steel plate, the softer plate reacted to squeeze the bushing to hold the bushing in position. The squeezing action is manifested on the outside and through the walls of the bushing, on the inside diameter of the bushing, whereby the inside diameter of the bushing would be reduced by one half a thousandth of an inch on a concentricity dictated by the post in the fixture. Thus an accurate dimension and shape are obtained without the usual expensive manufacturing procedures.

Havin shown and described preferred embodiments of the present invention by way of example, it should be realized that structural changes could be made and other examples given Without departing from either the spirit or scope of this invention.

What I claim is:

l. A bushing for use in a die set comprising a hollow body member having a longitudinal axis and provided with a plurality of helical serrations, an entering end on the outside diameter of one end of said hollow body member, said entering end having a diameter reduced 6 by a dimension approximating one-half the normal depth of said helical serrations and parallel to said longitudinal axis.

2. A bushing for use in a die set comprising a hollow body member approximating one inch on the inside diameter and having a longitudinal axis and provided with a plurality of helical serrations approximately seventeenthousandths of an inch deep on the outside diameter, a plain lead surface on the outside diameter of one end of said bushing, an entering end on the outside diameter adjacent said plain lead surface, sa d entering end having a length of approximately ten-thousandths of an inch long, said entering end having a recess approximating one-half the normal depth of said helical serrations and parallel to said longitudinal axis.

3. A carbonitride hardened bushing for use in a die set comprising a hollow longitudinal body member provided with a plurality of helical serrations on the outside diameter, a plain lead surface on the outside diameter of one end of said bushing, an entering end on the outside diameter adjacent said plain lead surface, said entering end having a recess approximately one-half the normal depth of said helical serrations and parallel to said hollow longitudinal body member.

4. A bushing for use in a die set comprising a hollow longitudinal body member provided with a plurality of helical serrations on the outside diameter and having a pitch and depth approximating a number twelve thread, American Society of Automotive Engineers Standard, an entering end having a recess approximately one-half the normal depth of said serrations, said recess being parallel to said hollow longitudinal body member.

5. The method of assembling bushings in a die set which includes the steps or" providing openings in a die holder and aligned openings in a punch holder, placing said punch and die holders in a fixture having master guide posts, placing bushings on said master guide posts and closing the fixture to drive the bushings into said openings.

6. The method of assembling bushings in a die set which includes the steps of providing openings in a die holder and aligned openings in a punch holder, placing said punch and die holders in a fixture having master guide posts, placing bushings having helically serrated outer surfaces on said master guide posts and then closing the fixture to drive the bushings into said openings ith an axial and rotating motion to center them in axial alignment with the guide posts.

7. The method of assembling a plurality of bushings in a die set which includes the steps of providing helical serrations on the outside diameter of the bushings, carbonitride hardening the bushings, and providing openings in a die holder and aligned openings in a punch holder, placing a fixture in a vertical press, placing said die and punch holders in a fixture having master guide posts, placing said bushings on said master guide posts, and then actuating said vertical press to close said fixture to drive said bushings simultaneously into said openings with an axial and rotating motion to center said bushings in axial alignment with said guide posts and to provide said bushings on the inside diameter with the shape and size of said guide posts.

8. The method of assembling a plurality of hollow body members in a die set which includes the steps of providing each hollow body member with a longitudinal axis and with a plurality ofhelical serrations on the outside or" each hollow body member, an entering end on the outside diameter of one end of each hollow body member, the entering end having a diameter reduced by a dimension approximating one half the normal depth of the helical serrations, the entering end having a contour parallel to a longitudinal axis, carbonitride hardening each hollow body member, providing openings in a die holder and aligned openings in a punch holder, placing a fixture in References (Iited in tire file of this patent a vertic al ress, placing said die and punch holders in 21 UNITED STATES PATENTS fixture having master guide posts, placing a hollow body member on each of said master guide posts, and then 1,459,793 1911115911 et 1923 actuating said vertical press to close said fixture to drive 5 1,700,139 smith 22, 1929 said hollow body members simultaneously into said open- 1,750,544 W flier 1930 ings with an axial and rotating motion to center each 2,180,282 Leighton Nov. 14, 1939 hollow body members in axial alignment with the guide 2,180,283 Leighton NOV. 14, 1939 posts and to provide each hollow body member on the 2,891,302 Fuglie et al. June 23, 1959 inside diameter with the shape ar d size of the guide post. 10 3,067,509 Welles Dec. 11, 1962 

5. THE METHOD OF ASSEMBLING BUSHINGS IN A DIE SET WHICH INCLUDES THE STEPS OF PROVIDING OPENINGS IN A DIE HOLDER AND ALIGNED OPENINGS IN A PUNCH HOLDER, PLACING SAID PUNCH AND DIE HOLDERS IN A FIXTURE HAVING MASTER 